This invention relates generally to filters and more particularly to throttling feed apertures commonly known a slices.
In various devices such as filters of slurries, in particular slurries of fibrous materials such as papermaking pulp, throttling feed apertures are employed to break down clumps of fiber known commonly as "flocs". To accomplish this, throttling feed apertures provide a desired exit velocity and promote uniform distribution across the length of the device. A typical prior art feed manifold with fixed slice exit is shown in FIG. 1 and FIG. 2 of the attached drawings. Such manifolds are often fed with excess flow, such excess flow being recirculated to enhance uniformity and avoid stagnation which might occur in a dead headed chamber. Net flow through the slice is then the total flow entering the manifold minus the excess flow which is recirculated. Fixed slice openings, however, lack versatility in feed selection and are subject to plugging and cannot be unplugged during operation. FIG. 3 shows a typical prior art fixed slice. FIG. 3A shows a variable slice of a prior art type mounted in a side distribution channel 25.
Hithertofore variable slices have been purged of plugs by opening the slice exit to its wide open position to allow the plug material to be forced out. This is a significant drawback since the released plug material can only pass into the filter or like downstream apparatus which can cause significant damage to drum surfaces or product, etc. and/or reduce the performance of the filter to form a pulp mat when the plug material is too large to pass small narrow openings in the filter structure e.g., compacting baffle tip openings.
The foregoing illustrates limitations known to exist in present devices. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.